CA1115019A - Elastomeric body - Google Patents
Elastomeric bodyInfo
- Publication number
- CA1115019A CA1115019A CA308,609A CA308609A CA1115019A CA 1115019 A CA1115019 A CA 1115019A CA 308609 A CA308609 A CA 308609A CA 1115019 A CA1115019 A CA 1115019A
- Authority
- CA
- Canada
- Prior art keywords
- swelling agent
- process according
- elastomeric body
- approximately
- swelling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/02—Chemical treatment or coating of shaped articles made of macromolecular substances with solvents, e.g. swelling agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/0009—After-treatment of articles without altering their shape; Apparatus therefor using liquids, e.g. solvents, swelling agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/14—Anti-skid inserts, e.g. vulcanised into the tread band
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2021/00—Use of unspecified rubbers as moulding material
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Tires In General (AREA)
- Treatments Of Macromolecular Shaped Articles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a process for increasing the abrasion resistance of a vulcanized elastomeric body, such as a tire, V-belt, conveyor belt, hose, spring element, or floor cover, by changing the state of stress, wherein the elastomeric body is at least partially treated with a swelling agent, i.e. a medium soluble in the elastomer.
The invention provides a process for increasing the abrasion resistance of a vulcanized elastomeric body, such as a tire, V-belt, conveyor belt, hose, spring element, or floor cover, by changing the state of stress, wherein the elastomeric body is at least partially treated with a swelling agent, i.e. a medium soluble in the elastomer.
Description
T]~e present invention relatcs to a process Eor increasing ~he abrasion resistance of a vulcanized elastomeric body, for example, of a tire, V-belt, conveying belt, spring el~ment, hose, floor cover, or the like, by changiny the state of stress.
In a known process for increasing the abrasion resistance of rubber tires, the tread and -the carcass are produced and vul-cani~ed separately, the diameter of the tread ring being of a slightly larger size than the ring of -the carcass. By applying great pressure on the entire tread ring an intimate bond with the tire carcass is attained. This results in a compression and in substantial compressive stresses in the tread ring whereby the abrasion resistance of the tread is substantially improved.
The problem underlying the present invention is to devise a process with the same aim but in a more rational manner and particularly for the quality in a better manner so that other elastomeric products exposed to increased abrasion can also benefit from the same effect.
According to the lnvention the process lies in that the elastomeric body is at least partially treated with a swelling agent, i.e. a medium soluble in the elastomer.
The resulting effect is such that the swelling-agent molecules arranged in the polymer structure of the cross-linked elastomer enlarge the interval between adjacent points of cross-linking as compared with the interval formed by tl~e cross-linking reaction so that the polyr~er chains are stretched. ~
It has been found that elastomeric bodies having the feature according to the invention have a higher resilience and a better low-temperature flexibility than elastomeric bodies which also contain a swelling agent but with the difference that the swelling agent had been incorporated prior to the vulcanization so that no stretching, i.e., spacing of the points of cross-linking occurs as compared with the structure of the po~ymer chains which ,'r4~
~resul~s from the s-tate of cross-linking. This improvement of the proper~y is illus~rated by rrable 1 for a natural rub~er mix~ure.
It is evident from Table 1 that the listed physical properties of the MixtUre C are be~ter than those of the mixture B
although the formulae of these mixtures are identical. Strength, moc1ulus, resilience and hardness are higher. The values for abrasion and the f~exometer tes~ are lower. AnalogOus tests were also carried out with other elastomer types and showed the same trends throughout.
At dynamic stress this higher resilience results in a lower hysteresis and thus in less heating of the elas~omeric body.
This fact can be utilized in the most diverse elastomeric bodies, for example, in pulleys for cable railways, synthetic rubber tubes ~ -or hoses, hand rails for escalators, etc. This ef~ect can be explained, at least to some extent, in that because of the present more extended structure the rotation about the C-C single bond is easier, i.e., that the intensity of activity required for over-coming the potential difference is lower.
However, since the manner of space arrangement of the polymer chains is fixed per se by the cross-linking and corresponds ~-approximately to a state of equilibrium under the conditions of production, all the polymer chains which are further stretched due to the force of the swelling agent also tend to resume their orig-inal tangled position. This trénd is compensated by khe swelling agent which penetrates between two points of cross-linking so that at isotropic swelling no stress is evident on the outside.
A uniform wetting of all the surface portions even of an elastomeric body haviny a complex shape can be attained by carrying out the treatment by immersion so that, if required, only specific portions of the elastomeric body are wetted. For example, only a specific portion of an elastomeric body can be immersed while the .
remaining portion thus remains substantially free from swelling ~
In a known process for increasing the abrasion resistance of rubber tires, the tread and -the carcass are produced and vul-cani~ed separately, the diameter of the tread ring being of a slightly larger size than the ring of -the carcass. By applying great pressure on the entire tread ring an intimate bond with the tire carcass is attained. This results in a compression and in substantial compressive stresses in the tread ring whereby the abrasion resistance of the tread is substantially improved.
The problem underlying the present invention is to devise a process with the same aim but in a more rational manner and particularly for the quality in a better manner so that other elastomeric products exposed to increased abrasion can also benefit from the same effect.
According to the lnvention the process lies in that the elastomeric body is at least partially treated with a swelling agent, i.e. a medium soluble in the elastomer.
The resulting effect is such that the swelling-agent molecules arranged in the polymer structure of the cross-linked elastomer enlarge the interval between adjacent points of cross-linking as compared with the interval formed by tl~e cross-linking reaction so that the polyr~er chains are stretched. ~
It has been found that elastomeric bodies having the feature according to the invention have a higher resilience and a better low-temperature flexibility than elastomeric bodies which also contain a swelling agent but with the difference that the swelling agent had been incorporated prior to the vulcanization so that no stretching, i.e., spacing of the points of cross-linking occurs as compared with the structure of the po~ymer chains which ,'r4~
~resul~s from the s-tate of cross-linking. This improvement of the proper~y is illus~rated by rrable 1 for a natural rub~er mix~ure.
It is evident from Table 1 that the listed physical properties of the MixtUre C are be~ter than those of the mixture B
although the formulae of these mixtures are identical. Strength, moc1ulus, resilience and hardness are higher. The values for abrasion and the f~exometer tes~ are lower. AnalogOus tests were also carried out with other elastomer types and showed the same trends throughout.
At dynamic stress this higher resilience results in a lower hysteresis and thus in less heating of the elas~omeric body.
This fact can be utilized in the most diverse elastomeric bodies, for example, in pulleys for cable railways, synthetic rubber tubes ~ -or hoses, hand rails for escalators, etc. This ef~ect can be explained, at least to some extent, in that because of the present more extended structure the rotation about the C-C single bond is easier, i.e., that the intensity of activity required for over-coming the potential difference is lower.
However, since the manner of space arrangement of the polymer chains is fixed per se by the cross-linking and corresponds ~-approximately to a state of equilibrium under the conditions of production, all the polymer chains which are further stretched due to the force of the swelling agent also tend to resume their orig-inal tangled position. This trénd is compensated by khe swelling agent which penetrates between two points of cross-linking so that at isotropic swelling no stress is evident on the outside.
A uniform wetting of all the surface portions even of an elastomeric body haviny a complex shape can be attained by carrying out the treatment by immersion so that, if required, only specific portions of the elastomeric body are wetted. For example, only a specific portion of an elastomeric body can be immersed while the .
remaining portion thus remains substantially free from swelling ~
- 2 - 7 '.. ~A . . :
_able 1 (All the measurements at room temperature~
. agent mixed agent seeped A without in prior in after the Mixture* swelling to the vul- vulcanizàtion agent can zation (10~ by _ _ _ ;., strength (kp/sq cm 209 ]63 194 (DIN 53504 from 8/75 _ __ _ __ modulus (150 kp/sq cm) (DIN 53504 from 33 21 27 _ 3 _ _ _ a~rasion (mm ~ 114 72 -(DIN 53516 from 1/77) 65 _ resilience (~)- 38 42 48 (DIN 53512 from 6/77) _ flexometer /TC 4 116 69 (DIN 53533 from 8/75) 3 _ hardness (Sh A) 64 55 56 (DIN 53505 from 8/73) * pure natural rubber quality; vulcanizate at 160C/15 min., size of test specimen according to DIN standard.
** swelling agent = dioctyl adipate + 1.5% of anti-oxidant +
I.5% of wax, content of'swelling agent 10% by weight.
*** seeping conditions: 80C -_____________________ agent. However, it is also possible to carry out the treatment with the swelling agent by spraying, spreading, roller-coating and khe like.
In order to attain a distribution as uniform as possible in the desired portion of the elastomeric body, the treatment with the swelling agent may be followed by a period of storage, if required at elevated temperature. This is a quasi-tempering pro-cedure, which may also occur at room temperature if the viscosityof the swelling agent used, and the type of elastomer permits this.
In very special cases, the measure of supplementing a . ~
~, .
,welling ayent component in a mix~ure (which was referred to here-inbefore as disadv~n-tageous for the process) can be favourable, i.e., in cases when at: identical solubi]ity but different rates of dif~
fusion the s~rength of a component of the swelliny agent is reduced. ~
In such a case it is appropriate to check the composition of the :
swelling agent regularly and, if required, to replenish impoverished components of the swelling agent.
For the production of a tire according to -the invention it is advantageous if the treatment with the swelling agent is -~
carried out for approximately l to approximately lO hours, prefer .
ably for approximately 4 to approximately 7 hours at approxirnately 50 to approximately 100C, preferably at approximately 70 to approx-imately 90C. These conditions apply particularly to the above-mentioned diesters of aliphatic and aromatic dicarboxylic acids, trialkyl and triaryl phosphates, diaryl ethers as well as mineral oils and spindle oils. Depending on the elastomer, particularly dioctyl adipate, dioctyl sebacate, dioctyl phthalate, tricresyl phospliate and spindle oil are preferably used. As mentioned here-inbefore, the treatment with the swelling agent may be followed by tempering. The time of swelling and tempering can be kept short in that the treatment with the swelling agent is carried out in an apparatus having a suitable temperature.
A problem encountered again and again in the dynamic stress of elastomeric bodies, as for example, V-belts, tires, pulleys for cable railways or the like, is the growth to which these articles are subject while they are used. The growth is due to some extent to the fact that these articles are not in the optimum state of equilibrium of the reinforcing layers which corresponds ~`
to the use. It has now been found that a particularly good, at least partial remedy can be obtained by the measures of the present invention if the elastomeric body is treated in the state of stress in which it is used, i.e., in the treatment according to the inven-. - . c~ .
-~: tion wi~h swelling ~gent the tire is to be acted upon wi~h the internal pressure under which it is used~ a V-belt is to be treated with corresponding standard stress, etc. Then, even during the treatment with the swelling agent said growth occurs to which the article normally is subject while in use so that this negative effec-t can be at least partially anticipated and thus be taken into ~ --account. rrhis can be done in s-uch a way that the elastomeric body to be cross-linked is produced in a correspondingly smaller size, whereby the growth occurring during the swelling has already been taken into account for the final size of the elastomeric body.
The requirements to be met by the abrasi~n resistance of floor covers, container linings, or the like, often are quite substantial. Therefore, it has been obvious to extend the process according to the invention to these types of elastomeric bodies as well. A development of the invention which is particularly exped-ient in this respect provides for a floor cover, a container lining, or the like, that, after the incorporation of the swelling agent, the latter is polymerized either with itself and/or with a compon-ent of the elastomer or with another mixture component. As mentionec hereinbefore, the initial stress effect caused by the swelling is fixed by the polymerization. For covers not adhering to the floor it is expedient to apply the process according to the invention on ``
both sides in order to avoid warping of the cover.
A special efect is obtained if reinforcing elements, for example, wires, textile or synthetic threads, sheet metal, plastics sheets, rigid structural members, or the like, in which the swelling agent used has substantially no solubility are fixed on or in the elastomeric body. In this kind of arrangement the swelling agent applied can cause only an anisotropic expansion of the elastomer.
However, because of their isotropy elastomers tend to expand uniformly in all directions so that compressive stresses .
dre buil~ up if t~is is not possible. A number of physical prop-erties are thus improved as compared with elastomeric bodies into ~;
which the swelling agent has been mixed~ ~ -In addition to the advantage of building up compressive `
stresses in the elastomeric body, there is a furthex advantage, namely that these compressive stresses in the elastomer act as tensile stresses on ~he reinforcing elements. The service life of these elastomeric bodies is thus substantially extended si`nce wires, textile or synthetic threads, or the like, work much more favour-ably under stretching strainj whereas if pressure is exerted onthem, this can cause compression, which can result in rupture and thus in loss of operability. These e~fects are important particularly in tires and V-belts, where the reinforcing elements are stressed particularly with respect to compression in the course of the rapid dynamic alternating stress.
The same effect like that occurring if reinforcing ; ~ ?
elements are provided in the elastomeric body also occurs if the elastomeric body contains swelling agents only in the zone near ~ the surface. In this zone compressive stresses are then built up since the subjacent portion of the elastomeric body is non-swollen.
Such an elastomeric body can also consist of an elastomer nucleus and an elastomer skin composed of different materials so that by selecting a specific swelling agent which is soluble only in the skin of the elastomeric body the desired inhomogeneity oE the swelling-agent distribution is réalized,in a particularly drastic way.
I an elastomer is from the group of natural rubber, butadiene rubber, styrene-butadiene rubber, then it is expedient to use a swelling agent from the group of diesters of aliphatic dicarboxylic acids, trialkyl phosphates, diaryl ether, ether thio~
ether or to use a mineral oil. When using elastomers such as chloroprene or acrylo-nitrile butadiene rubber the swelling ayents ' . ~ s , nentioned hereinbe~ore, wl~h the exception of mineral oil, are also --suitable. ~loreover, in this case triaryl phosphate, diesters of aromatic dicarboxylic acids or alkyl sulphonic esters can also be used.
Since the inclusion of swelling-agent molecules in the cross-linked elastomeric body is a diffusion process, the viscosity of the swelling agent is of course very important for the time slope. It is expedient that the kinematic viscosity of the swelling agent ~t 20C is below approximately 100 cSt. Even in the case of relatively large elastomeric bodies into which a substantial proportion of swelling agent is to diffuse a maximum swelling time of several hours is economically still acceptable. In this connec-tion it should also be mentioned that the vapour pressure of the swelling agent also is important. If the vapour pressure is relatively high, then, depending on the temperatures applied, there is a danger that the swelling agent diffuses out again and evapor-ates. Therefore, the correct choice of the suitahle swelling agent must be consideréd separately from case to case.
In order to prevent certain fillers present in the elastomeric body from being dissolved out by the action of the - swelling agent and thus from displaying their action in the elasto-- meric body any longer and from changing ~he intended composition of the swelling agent, it is advantageous to add fillers, for example, anti-oxidants, waxes, or the like, to the swelling agent. The selection of the fillers depends on the composition of the elasto-meric body. The above fillers anti-oxidants and waxes are charact-eristic of rubber mixtures. These anti-oxidants are, for example, p-phenylene diamines or condensation products of acetone and diphenylamine. E'requently used substances are N-isopropyl-N'-phenyl-p-phenylene diamine and phenyl-~-naphthyl amine. The waxes used are aliphatlc hydrocarbons which are primarily straight-chain and comprise a range of approximately C14-C60. The maximum of the molecular-weight distribution is at C30.
~;,i .
.. , .. , , , . ~ ~.
If special eEfects are to be attained, then it is advantageous to use, as the swelling agent, a mixture of two or more liquids which seep into the elastomer approximately equally fast. ~ diversified swelling can thus be at-tained in different layers of the vulcanizate, if required, whereby it can be possible to influence the desired properties favourably. The alto~ether equally fast infil-tration of the components used is impor-tant in cases in which it is intended to use the same swelling-agent bath for preparing several elastomeric bodies since otherwise care must be taken that the composition of the swelling a~ent is continuousl~
rechecked and that components are replaced if required. Moreover, there also is the danger that a swelling-agen-t component carried along initially will diffuse out again due -to segre-3a~ion and that the properties of the elastomeric body thus are subject to chan~e in the course of its use.
The application of the present invention to rubber -articles in the form of tires is particularly important. In this case, it is advantageous to treat the elastomeric body with swelling agent only in amounts required for swelling the zone 7 ' ' near the surface. The progressive initial stress effect described hereinbefore is then obtained. Therefore, these tires have an excellent abrasion behaviour which can be improved by up to and more than 50~ as compared with conventional tires. The improved abrasion characteristic is due to the ~act that the resistance to tear propagation with respect to cuts and damage in the tread is much better than in that of tires not designed accordin~ to the invention. This is demonstrated by the fact that a cut made in the tread does not spread apart bu-t remains substantially closed or the sides of the cut are even compressed. Since the tear 30 propagation is one oE the properties which determines the abrasion ~`~
behaviour, the abrasion of tires can be substantially improved by the use of the present invention.
. .
5~
In this connec-tion a further important acco~panying factor of -the pre~ent invention must be mentioned. In arl article such as a ~ire, a V-belt or a conveyor belt, in which if re~luircd, reinforeincJ layers of parallel threads, or the like, are present, shifting of the reinforcing elements occurs. This shiftincJ proces~
causes the article to get c]oser to its state of equilibrium. For example, this ean result in an angular displaeement oE fll)rie inserts of tires, whereby the eircumference of the tire can grow by a few percent. ~s in well-known the SaMe effect is also encoun-tered in V-belts. ~s mentioned hereinbefore in connection Wit]l tl increased resilience of elastomeric bodies designed according to the invention, this is a case o~ increased mobi]i-ty of the polymer chains. Ilowever, at the same time tensile s-tresses from the swollen elastomerie body aet on its reinforeing layers. These tensile stresses thus ean bring about a ehange of position of the reinforeing elements whieh eontributes to a relaxation. As des-eribed in greater detail hereafter, this ef~ect is encountered particularly if the swelling agent acts on the elastomeric body in a state corresponding to its state of load when in use.
The present invention is partieularly effeetive if the tire has a tread profile with projeetions extending beyond the eireumferenee. These projeetions ean be eontinuous pattern ri.ngs over the entire eireumferenee of the tire. In this ~ind o~ pattern the ineorporation o~ the swelling agent in tlle eireumEerential direetion ean produee no substantial inerease in volume so that a maximum eompressive initial stress in this direetion is attainable.
In a tread pattern eonsisting of individual profile bloeks tllis effeet would not be present to the same extent sinee eaeh profile bloek ean eseape into the adjaeent profile groove while enlarging the volume so that the important eompressive initial stress effeet, whieh is brought about by the interaetion of the non-flexible reinforeing inserts with the rubber having swelling properties, cannot be fully attained~ llowever, cases of uses of tires are known in w~lich there is a particular st~ess of profile projections extending approximately in an axial direction. In this casc the w~ar of this kind of profile projections can also be substantially reduced by using the invention.
The process according to the invention for producing an ~ ?
elastomeric body provides that the finished cross-linked elastomeric body, for example, the finished vulcanized rubber body, is treated with swelling agent while heating if required. secause of the solubility of the swelling agent in -the elastomer it penetrates between the polymer chains and thus increases the interval between the points of cross-linking.
The invention is explained hereafter in greater detail by means of examl~les with reference to the drawings in which Figure 1 shows an elastomeric body without reinforcing elements, Figures 2and 3 show an elastomeric body with reinforcing elements, Figure 4 shows a diagrammatic representation of a section ;
of a polymer chain~
Figures5 and 5a show a section of an elastomeric body provided with reinforcing elements and having a cut, and ;
Figure 6 shows a favourable tire profile according to ;
the invention.
A cube of an elastomeric boay is shown in Figure 1, in the non-swollen state 1 and in the swollen state 1'. On incorpora-ting a swelling agent in a non-reinforced elastomeric body the latter isotropically grows equally in all directions. Contrary to a widespread view the properties of a swollen elastomeric body are notnecessarily poorer in every respect than those o~ a non-swollen elastomeric body. On the contrary it has been surprisingly found ~;
that the resilience and the low temperature flexibility ., ~,~ , .
A~ h. . . ~:.
can be increased by incorporating swelling ayents.
An elastomeric body with reinforcing sheet metal 3 is shown in Figure# 2 in the non-swollen state 2 ànd in the swollen state 2'. The incorporation of the swelling agent results in an increase in volume of the elastomeric body, the attained dash-line contour corresponds to the amount of incorporated swelling agent.
At the centre of this kind of e~astomeric body isotr~pic swelling is not possible but only growth in height since the elastomeric body 2 is rigidly fixed to the reinforcing sheet iron 3, which cannot swell. Figure 3 shows the elastomeric body in the non-swollen state 2 in perspective, an approximately square surface element has been drawn superficially. Equally great compressive stresses aD act on this surface element from all sides. A number of cases of buildlng up compressive stresses in a layerof acomposite body are known from other fields of technology.
A layer of enamel applied on a metal sheet is an example.
By the contraction of the warm metal sheet on cooling the enamel layer is subjected to compressive stress. This is very important for the useability of these articles since the capacity o~the enamel to withstand tensile stress is not particularly great.
The hardening process when nitrating steel can be interpreted in an analogous way. Nitrogen diffuses into the surface of the heated steel body while expansion in lattice space occurs in this di~fusion zone. This can result in the build-up of compressive stresses in the nitrated layer and in tensile stresses in the subjacent layer.
A section of a polymer structure is shown in Figure 4.
In the non-swol`len state the polymer chain 5 between the cross-linking points 4 is very tangled. However, after the swelling the cross-linking points 4' spread apart while the polymer chain 5' is stretched.
The build-up of compressive stresses in an elastomeric ~ .
~,. . .
~. . ........................................................... . . .
5'~
body, whicll is fixed to a reinforcing sheet iron ' can be demon-strated by ma~ing a cut 6'. While a cut 6 in an elastomeric l~ody 2 is spread apart prior to the swellin~J the sides of a c~t 6' in an elastomeric body 2' are com2ressed after -thc swelling.
~ srnall amount of swelling ayent at least does not cause the cut 6' to spread apart.
The tire 7 shown in Figure 6 has a rin~3 pattern, which extends over the circumference. This kind of tread profile is particularly suitable for the use of the present process since particularly large compressive stresses can be built up by -the closed c~rcumEerential profile in the clrcumEerential direction.
;`
;: , ' ., .:.
~
. . ,
_able 1 (All the measurements at room temperature~
. agent mixed agent seeped A without in prior in after the Mixture* swelling to the vul- vulcanizàtion agent can zation (10~ by _ _ _ ;., strength (kp/sq cm 209 ]63 194 (DIN 53504 from 8/75 _ __ _ __ modulus (150 kp/sq cm) (DIN 53504 from 33 21 27 _ 3 _ _ _ a~rasion (mm ~ 114 72 -(DIN 53516 from 1/77) 65 _ resilience (~)- 38 42 48 (DIN 53512 from 6/77) _ flexometer /TC 4 116 69 (DIN 53533 from 8/75) 3 _ hardness (Sh A) 64 55 56 (DIN 53505 from 8/73) * pure natural rubber quality; vulcanizate at 160C/15 min., size of test specimen according to DIN standard.
** swelling agent = dioctyl adipate + 1.5% of anti-oxidant +
I.5% of wax, content of'swelling agent 10% by weight.
*** seeping conditions: 80C -_____________________ agent. However, it is also possible to carry out the treatment with the swelling agent by spraying, spreading, roller-coating and khe like.
In order to attain a distribution as uniform as possible in the desired portion of the elastomeric body, the treatment with the swelling agent may be followed by a period of storage, if required at elevated temperature. This is a quasi-tempering pro-cedure, which may also occur at room temperature if the viscosityof the swelling agent used, and the type of elastomer permits this.
In very special cases, the measure of supplementing a . ~
~, .
,welling ayent component in a mix~ure (which was referred to here-inbefore as disadv~n-tageous for the process) can be favourable, i.e., in cases when at: identical solubi]ity but different rates of dif~
fusion the s~rength of a component of the swelliny agent is reduced. ~
In such a case it is appropriate to check the composition of the :
swelling agent regularly and, if required, to replenish impoverished components of the swelling agent.
For the production of a tire according to -the invention it is advantageous if the treatment with the swelling agent is -~
carried out for approximately l to approximately lO hours, prefer .
ably for approximately 4 to approximately 7 hours at approxirnately 50 to approximately 100C, preferably at approximately 70 to approx-imately 90C. These conditions apply particularly to the above-mentioned diesters of aliphatic and aromatic dicarboxylic acids, trialkyl and triaryl phosphates, diaryl ethers as well as mineral oils and spindle oils. Depending on the elastomer, particularly dioctyl adipate, dioctyl sebacate, dioctyl phthalate, tricresyl phospliate and spindle oil are preferably used. As mentioned here-inbefore, the treatment with the swelling agent may be followed by tempering. The time of swelling and tempering can be kept short in that the treatment with the swelling agent is carried out in an apparatus having a suitable temperature.
A problem encountered again and again in the dynamic stress of elastomeric bodies, as for example, V-belts, tires, pulleys for cable railways or the like, is the growth to which these articles are subject while they are used. The growth is due to some extent to the fact that these articles are not in the optimum state of equilibrium of the reinforcing layers which corresponds ~`
to the use. It has now been found that a particularly good, at least partial remedy can be obtained by the measures of the present invention if the elastomeric body is treated in the state of stress in which it is used, i.e., in the treatment according to the inven-. - . c~ .
-~: tion wi~h swelling ~gent the tire is to be acted upon wi~h the internal pressure under which it is used~ a V-belt is to be treated with corresponding standard stress, etc. Then, even during the treatment with the swelling agent said growth occurs to which the article normally is subject while in use so that this negative effec-t can be at least partially anticipated and thus be taken into ~ --account. rrhis can be done in s-uch a way that the elastomeric body to be cross-linked is produced in a correspondingly smaller size, whereby the growth occurring during the swelling has already been taken into account for the final size of the elastomeric body.
The requirements to be met by the abrasi~n resistance of floor covers, container linings, or the like, often are quite substantial. Therefore, it has been obvious to extend the process according to the invention to these types of elastomeric bodies as well. A development of the invention which is particularly exped-ient in this respect provides for a floor cover, a container lining, or the like, that, after the incorporation of the swelling agent, the latter is polymerized either with itself and/or with a compon-ent of the elastomer or with another mixture component. As mentionec hereinbefore, the initial stress effect caused by the swelling is fixed by the polymerization. For covers not adhering to the floor it is expedient to apply the process according to the invention on ``
both sides in order to avoid warping of the cover.
A special efect is obtained if reinforcing elements, for example, wires, textile or synthetic threads, sheet metal, plastics sheets, rigid structural members, or the like, in which the swelling agent used has substantially no solubility are fixed on or in the elastomeric body. In this kind of arrangement the swelling agent applied can cause only an anisotropic expansion of the elastomer.
However, because of their isotropy elastomers tend to expand uniformly in all directions so that compressive stresses .
dre buil~ up if t~is is not possible. A number of physical prop-erties are thus improved as compared with elastomeric bodies into ~;
which the swelling agent has been mixed~ ~ -In addition to the advantage of building up compressive `
stresses in the elastomeric body, there is a furthex advantage, namely that these compressive stresses in the elastomer act as tensile stresses on ~he reinforcing elements. The service life of these elastomeric bodies is thus substantially extended si`nce wires, textile or synthetic threads, or the like, work much more favour-ably under stretching strainj whereas if pressure is exerted onthem, this can cause compression, which can result in rupture and thus in loss of operability. These e~fects are important particularly in tires and V-belts, where the reinforcing elements are stressed particularly with respect to compression in the course of the rapid dynamic alternating stress.
The same effect like that occurring if reinforcing ; ~ ?
elements are provided in the elastomeric body also occurs if the elastomeric body contains swelling agents only in the zone near ~ the surface. In this zone compressive stresses are then built up since the subjacent portion of the elastomeric body is non-swollen.
Such an elastomeric body can also consist of an elastomer nucleus and an elastomer skin composed of different materials so that by selecting a specific swelling agent which is soluble only in the skin of the elastomeric body the desired inhomogeneity oE the swelling-agent distribution is réalized,in a particularly drastic way.
I an elastomer is from the group of natural rubber, butadiene rubber, styrene-butadiene rubber, then it is expedient to use a swelling agent from the group of diesters of aliphatic dicarboxylic acids, trialkyl phosphates, diaryl ether, ether thio~
ether or to use a mineral oil. When using elastomers such as chloroprene or acrylo-nitrile butadiene rubber the swelling ayents ' . ~ s , nentioned hereinbe~ore, wl~h the exception of mineral oil, are also --suitable. ~loreover, in this case triaryl phosphate, diesters of aromatic dicarboxylic acids or alkyl sulphonic esters can also be used.
Since the inclusion of swelling-agent molecules in the cross-linked elastomeric body is a diffusion process, the viscosity of the swelling agent is of course very important for the time slope. It is expedient that the kinematic viscosity of the swelling agent ~t 20C is below approximately 100 cSt. Even in the case of relatively large elastomeric bodies into which a substantial proportion of swelling agent is to diffuse a maximum swelling time of several hours is economically still acceptable. In this connec-tion it should also be mentioned that the vapour pressure of the swelling agent also is important. If the vapour pressure is relatively high, then, depending on the temperatures applied, there is a danger that the swelling agent diffuses out again and evapor-ates. Therefore, the correct choice of the suitahle swelling agent must be consideréd separately from case to case.
In order to prevent certain fillers present in the elastomeric body from being dissolved out by the action of the - swelling agent and thus from displaying their action in the elasto-- meric body any longer and from changing ~he intended composition of the swelling agent, it is advantageous to add fillers, for example, anti-oxidants, waxes, or the like, to the swelling agent. The selection of the fillers depends on the composition of the elasto-meric body. The above fillers anti-oxidants and waxes are charact-eristic of rubber mixtures. These anti-oxidants are, for example, p-phenylene diamines or condensation products of acetone and diphenylamine. E'requently used substances are N-isopropyl-N'-phenyl-p-phenylene diamine and phenyl-~-naphthyl amine. The waxes used are aliphatlc hydrocarbons which are primarily straight-chain and comprise a range of approximately C14-C60. The maximum of the molecular-weight distribution is at C30.
~;,i .
.. , .. , , , . ~ ~.
If special eEfects are to be attained, then it is advantageous to use, as the swelling agent, a mixture of two or more liquids which seep into the elastomer approximately equally fast. ~ diversified swelling can thus be at-tained in different layers of the vulcanizate, if required, whereby it can be possible to influence the desired properties favourably. The alto~ether equally fast infil-tration of the components used is impor-tant in cases in which it is intended to use the same swelling-agent bath for preparing several elastomeric bodies since otherwise care must be taken that the composition of the swelling a~ent is continuousl~
rechecked and that components are replaced if required. Moreover, there also is the danger that a swelling-agen-t component carried along initially will diffuse out again due -to segre-3a~ion and that the properties of the elastomeric body thus are subject to chan~e in the course of its use.
The application of the present invention to rubber -articles in the form of tires is particularly important. In this case, it is advantageous to treat the elastomeric body with swelling agent only in amounts required for swelling the zone 7 ' ' near the surface. The progressive initial stress effect described hereinbefore is then obtained. Therefore, these tires have an excellent abrasion behaviour which can be improved by up to and more than 50~ as compared with conventional tires. The improved abrasion characteristic is due to the ~act that the resistance to tear propagation with respect to cuts and damage in the tread is much better than in that of tires not designed accordin~ to the invention. This is demonstrated by the fact that a cut made in the tread does not spread apart bu-t remains substantially closed or the sides of the cut are even compressed. Since the tear 30 propagation is one oE the properties which determines the abrasion ~`~
behaviour, the abrasion of tires can be substantially improved by the use of the present invention.
. .
5~
In this connec-tion a further important acco~panying factor of -the pre~ent invention must be mentioned. In arl article such as a ~ire, a V-belt or a conveyor belt, in which if re~luircd, reinforeincJ layers of parallel threads, or the like, are present, shifting of the reinforcing elements occurs. This shiftincJ proces~
causes the article to get c]oser to its state of equilibrium. For example, this ean result in an angular displaeement oE fll)rie inserts of tires, whereby the eircumference of the tire can grow by a few percent. ~s in well-known the SaMe effect is also encoun-tered in V-belts. ~s mentioned hereinbefore in connection Wit]l tl increased resilience of elastomeric bodies designed according to the invention, this is a case o~ increased mobi]i-ty of the polymer chains. Ilowever, at the same time tensile s-tresses from the swollen elastomerie body aet on its reinforeing layers. These tensile stresses thus ean bring about a ehange of position of the reinforeing elements whieh eontributes to a relaxation. As des-eribed in greater detail hereafter, this ef~ect is encountered particularly if the swelling agent acts on the elastomeric body in a state corresponding to its state of load when in use.
The present invention is partieularly effeetive if the tire has a tread profile with projeetions extending beyond the eireumferenee. These projeetions ean be eontinuous pattern ri.ngs over the entire eireumferenee of the tire. In this ~ind o~ pattern the ineorporation o~ the swelling agent in tlle eireumEerential direetion ean produee no substantial inerease in volume so that a maximum eompressive initial stress in this direetion is attainable.
In a tread pattern eonsisting of individual profile bloeks tllis effeet would not be present to the same extent sinee eaeh profile bloek ean eseape into the adjaeent profile groove while enlarging the volume so that the important eompressive initial stress effeet, whieh is brought about by the interaetion of the non-flexible reinforeing inserts with the rubber having swelling properties, cannot be fully attained~ llowever, cases of uses of tires are known in w~lich there is a particular st~ess of profile projections extending approximately in an axial direction. In this casc the w~ar of this kind of profile projections can also be substantially reduced by using the invention.
The process according to the invention for producing an ~ ?
elastomeric body provides that the finished cross-linked elastomeric body, for example, the finished vulcanized rubber body, is treated with swelling agent while heating if required. secause of the solubility of the swelling agent in -the elastomer it penetrates between the polymer chains and thus increases the interval between the points of cross-linking.
The invention is explained hereafter in greater detail by means of examl~les with reference to the drawings in which Figure 1 shows an elastomeric body without reinforcing elements, Figures 2and 3 show an elastomeric body with reinforcing elements, Figure 4 shows a diagrammatic representation of a section ;
of a polymer chain~
Figures5 and 5a show a section of an elastomeric body provided with reinforcing elements and having a cut, and ;
Figure 6 shows a favourable tire profile according to ;
the invention.
A cube of an elastomeric boay is shown in Figure 1, in the non-swollen state 1 and in the swollen state 1'. On incorpora-ting a swelling agent in a non-reinforced elastomeric body the latter isotropically grows equally in all directions. Contrary to a widespread view the properties of a swollen elastomeric body are notnecessarily poorer in every respect than those o~ a non-swollen elastomeric body. On the contrary it has been surprisingly found ~;
that the resilience and the low temperature flexibility ., ~,~ , .
A~ h. . . ~:.
can be increased by incorporating swelling ayents.
An elastomeric body with reinforcing sheet metal 3 is shown in Figure# 2 in the non-swollen state 2 ànd in the swollen state 2'. The incorporation of the swelling agent results in an increase in volume of the elastomeric body, the attained dash-line contour corresponds to the amount of incorporated swelling agent.
At the centre of this kind of e~astomeric body isotr~pic swelling is not possible but only growth in height since the elastomeric body 2 is rigidly fixed to the reinforcing sheet iron 3, which cannot swell. Figure 3 shows the elastomeric body in the non-swollen state 2 in perspective, an approximately square surface element has been drawn superficially. Equally great compressive stresses aD act on this surface element from all sides. A number of cases of buildlng up compressive stresses in a layerof acomposite body are known from other fields of technology.
A layer of enamel applied on a metal sheet is an example.
By the contraction of the warm metal sheet on cooling the enamel layer is subjected to compressive stress. This is very important for the useability of these articles since the capacity o~the enamel to withstand tensile stress is not particularly great.
The hardening process when nitrating steel can be interpreted in an analogous way. Nitrogen diffuses into the surface of the heated steel body while expansion in lattice space occurs in this di~fusion zone. This can result in the build-up of compressive stresses in the nitrated layer and in tensile stresses in the subjacent layer.
A section of a polymer structure is shown in Figure 4.
In the non-swol`len state the polymer chain 5 between the cross-linking points 4 is very tangled. However, after the swelling the cross-linking points 4' spread apart while the polymer chain 5' is stretched.
The build-up of compressive stresses in an elastomeric ~ .
~,. . .
~. . ........................................................... . . .
5'~
body, whicll is fixed to a reinforcing sheet iron ' can be demon-strated by ma~ing a cut 6'. While a cut 6 in an elastomeric l~ody 2 is spread apart prior to the swellin~J the sides of a c~t 6' in an elastomeric body 2' are com2ressed after -thc swelling.
~ srnall amount of swelling ayent at least does not cause the cut 6' to spread apart.
The tire 7 shown in Figure 6 has a rin~3 pattern, which extends over the circumference. This kind of tread profile is particularly suitable for the use of the present process since particularly large compressive stresses can be built up by -the closed c~rcumEerential profile in the clrcumEerential direction.
;`
;: , ' ., .:.
~
. . ,
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of increasing the wear resistance of a vulcanized elastomeric body containing at least one reinforcement element by changing its stress state, comprising providing an elastomeric body with at least one reinforcement element;
treating only part of the elastomeric body by impregnating said elastomeric body with a swelling agent comprising a medium which is soluble in the elastomer of the elastomeric body in an amount effective for swelling said treated portion; the distribution of the swelling agent diminishing from the surface of said treated part of the elastomeric body towards the reinforcement element.
treating only part of the elastomeric body by impregnating said elastomeric body with a swelling agent comprising a medium which is soluble in the elastomer of the elastomeric body in an amount effective for swelling said treated portion; the distribution of the swelling agent diminishing from the surface of said treated part of the elastomeric body towards the reinforcement element.
2. A process according to claim 1, wherein the treat-ment is carried out while heating.
3. A process according to claim 1, wherein the treat-ment is carried out by immersion.
4. A process according to claim 1 or claim 2, wherein the treatment is carried out by spraying, spreading, or roller-coating.
5. A process according to claim 1, wherein the treatment with swelling agent is followed by a period of storage at an elevated temperature.
6. A process according to claim 3, wherein the composition of the swelling agent is regularly checked and any impoverished components of the swelling agent are replenished.
7. A process according to claim 1, wherein reinforcing elements selected from wires, textile or synthetic threads, plastics sheets, or rigid structural members in which the swelling agent has substantially no solubility, are fixed to or in the elastomeric body.
8. A process according to claim 1, wherein the elasto-meric body is treated with a swelling agent in an amount required only for slight swelling in the zone near the surface.
9. A process according to claim 1, wherein after, seeping the swelling agent is caused to homopolymerize and/or copolymerize with a component of the elastomer or with another component.
10. A process according to claim 1, 2 or 3 wherein the swelling agent is selected from the group of diesters of aliphatic dicarboxylic acids, trialkyl phosphates, diaryl ethers, ether trioethers, and mineral oil or a mixture thereof.
11. A process according to claim 1, 2 or 3 wherein the swelling agent is selected from the group of triaryl phos-phates, alkyl sulphoesters, diesters of aromatic dicarboxylic acids or a mixture thereof.
12. A process according to claim 1, 2 or 3 wherein fillers are added to the swelling agent.
13. A process according to claim 1 in which antioxidants and/or waxes are added to the swelling agent.
14. A process according to claim 1, wherein the swelling agent is a mixture of two or more liquids, which seep equally fast into the elastomer.
15. A process according to claim 1, 2 or 3 in which the body is a tire, V-belt, conveyor belt, hose resilient element or floor covering.
16. A process according to claim 1 for changing the state of stress of a tire, wherein the treatment with the swelling agent is carried out by immersion for a period from approximately 1 to approximately 10 hours, at approximately 50 to approximately 100°C.
17. A process according to claim 16, wherein the treatment with the swelling agent is carried out from approximately 4 to approximately 7 hours at a temperature of approximately 70 to approximately 90°C.
18. A process according to claim 1, 2 or 3 wherein the treatment of the elastomeric body is carried out in the state of stress when said elastomeric body is being used.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH9576/77 | 1977-08-04 | ||
| CH957677A CH638232A5 (en) | 1977-08-04 | 1977-08-04 | ELASTOMER BODY. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115019A true CA1115019A (en) | 1981-12-29 |
Family
ID=4353434
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA308,609A Expired CA1115019A (en) | 1977-08-04 | 1978-08-02 | Elastomeric body |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4376667A (en) |
| BE (1) | BE869557A (en) |
| CA (1) | CA1115019A (en) |
| CH (1) | CH638232A5 (en) |
| DE (1) | DE2829157A1 (en) |
| FR (1) | FR2399458A1 (en) |
| GB (1) | GB2001998B (en) |
| IT (1) | IT1099004B (en) |
| NL (1) | NL7808118A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5840643U (en) * | 1981-09-12 | 1983-03-17 | 三菱電機株式会社 | Automotive V-belt |
| US4589223A (en) * | 1984-07-25 | 1986-05-20 | Johnson Fishing, Inc. | Fishing lure composition |
| FR2677367A1 (en) * | 1991-06-07 | 1992-12-11 | Delhomme Gilles | Process for self-adjustment with a liquid of rubbers in contact with a surface |
| CN114953523B (en) * | 2022-05-23 | 2023-10-13 | 湖北工业大学 | Method for reducing internal stress of polymer product |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US708823A (en) * | 1901-11-27 | 1902-09-09 | Oxylin Werke Actien Ges | Process of preparing and treating rubber-coated materials. |
| US2170919A (en) * | 1936-09-28 | 1939-08-29 | Cupples Company | Method of making rubber articles |
| US2393871A (en) * | 1941-12-22 | 1946-01-29 | Bay Chemical Company Inc | Vulcanized rubber hydrohalide |
| US3442689A (en) * | 1965-09-27 | 1969-05-06 | Grace W R & Co | Method of plasticizing rubber films |
| FR1483559A (en) * | 1966-06-16 | 1967-06-02 | Nii Rezinovoi Promy | Method of treating the surface of vulcanized rubbers |
| AU464814B2 (en) * | 1973-01-26 | 1975-09-04 | Bridgestone Tire Company Limited | A method for improving the adhering ability of vulcanized rubber surfaces |
-
1977
- 1977-08-04 CH CH957677A patent/CH638232A5/en not_active IP Right Cessation
-
1978
- 1978-07-03 DE DE19782829157 patent/DE2829157A1/en not_active Withdrawn
- 1978-07-19 US US05/926,222 patent/US4376667A/en not_active Expired - Lifetime
- 1978-07-20 IT IT25921/78A patent/IT1099004B/en active
- 1978-07-21 GB GB7830733A patent/GB2001998B/en not_active Expired
- 1978-07-28 FR FR7822772A patent/FR2399458A1/en active Pending
- 1978-08-02 CA CA308,609A patent/CA1115019A/en not_active Expired
- 1978-08-02 NL NL787808118A patent/NL7808118A/en not_active Application Discontinuation
- 1978-08-04 BE BE78189735A patent/BE869557A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| IT7825921A0 (en) | 1978-07-20 |
| CH638232A5 (en) | 1983-09-15 |
| US4376667A (en) | 1983-03-15 |
| GB2001998B (en) | 1982-02-17 |
| IT1099004B (en) | 1985-09-18 |
| NL7808118A (en) | 1979-02-06 |
| GB2001998A (en) | 1979-02-14 |
| BE869557A (en) | 1979-02-05 |
| DE2829157A1 (en) | 1979-02-15 |
| FR2399458A1 (en) | 1979-03-02 |
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